1. Field of the Invention
This invention concerns a novel car anti-theft device comprising a manually operable key fitted with illuminatable element means and a steering lock fitted with light sensitive element means.
2. Prior Art
Conventional car keys are identified by their specific shapes and numbers of key and groove serrations, respectively.
Therefore, the usable range of the keys must be highly limited and thus, picking possibilities are rather frequent.
In recent decades, however, improvements have been proposed to provide additional discriminating means in or on the key proper. As an example thereof, U.S. Pat. No. 4,148,372 may be referred to.
In this prior art device, a manually operable key is inserted into the steering lock and turned to the START-position. This is the first condition for starting the engine. An electric resistant pellet has been embedded in the material of the key. If the resistance value of the pellet is equal to a preset value specifically allocated to the car, it is adjudged that a correct manual key has been selected and used. This constitutes a second condition for starting the engine.
It has been found that the reliance on electric resistance is rather limitative for the identification of engine keys.
Further, the electric resistance will vary with variation of ambient temperature and humidity.